This invention relates to a motor-driven compressor and, more particularly, to a motor driven compressor for an air conditioning system where the compressor is cooled by refrigerant gas.
In the prior art, a compressor is usually incorporated in an automotive air conditioning system, and it is known to employ a motor-driven compressor in an automotive air conditioner.
Such a compressor is disclosed in Japanese Patent Provisional Publications No. 5-187356. This compressor is a swash type compressor that includes an electric motor and a refrigerant compressing device in a common housing. The electric motor is located in one part of the internal space of the housing, and the refrigerant compressing device is received in the remaining part of the housing. The electric motor and the refrigerant compressing device are arranged in the housing in a tandem relationship. The refrigerant compressing device includes cylinder bores, pistons located in the respective cylinder bores, a drive shaft and a swash plate coupled to the drive shaft for converting a rotational motion of the drive shaft to linear piston motion. A portion of the drive shaft supports a rotor of the electric motor. When the pistons slide within the cylinder bores, refrigerant is drawn into the cylinder bores. Compressed refrigerant is exhausted into an exhaust chamber. The electric motor is cooled by blow-by gases exhausted in an inner part of the housing and by heat dissipation through the walls of the housing. However, when the electric motor generates a large quantity of heat, the electric motor is not sufficiently cooled, which reduces a magnetic flux in the electric motor and reduces the motor""s efficiency.
Japanese Patent Provisional Publication No. 9-32729 discloses a scroll type compressor driven by an electric motor. In such a compressor, the electric motor and a refrigerant compressing device are located in first and second chambers of a common housing. Although the common housing has a partition wall between the electric motor and the refrigerant compressing device, the first and second chambers communicate with each other through a passage formed in the partition wall. An intake port is formed in the first chamber, and an exhaust port is formed in the second chamber. When the refrigerant compressing device is driven by the electric motor, refrigerant is drawn from the intake port into the refrigerant compressing device through the electric motor and the passage formed in the partition wall, compressed by the refrigerant compressing device, and exhausted from the exhaust port. The electric motor is cooled by refrigerant passing through a space between a stator and a rotor of the electric motor. In such a compressor, however, if the electric motor generates a large quantity of heat if the electric motor is operating under a high load, the temperature of the refrigerant becomes high with a resultant decrease in the compression efficiency.
It is an object of the present invention to provide a compressor that can effectively cool an electric motor in a highly reliable manner.
To achieve the above and other object, the present invention provides a compressor having an interior refrigerant passage. The refrigerant gas is supplied to the interior refrigerant passage from an external refrigerant circuit. The compressor comprises a housing, a cylinder bore disposed in the housing. A first chamber is disposed in the housing and communicates to the cylinder bore. A second chamber is disposed in the housing. The second chamber is partitioned from the first chamber in an air tight manner. A piston is movably located in the cylinder bore. A drive mechanism is disposed in the first chamber to move the piston. A motor is disposed in the second chamber to drive the drive mechanism. A refrigerant path connects the second chamber with the interior refrigerant passage.
Other aspect and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.